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  • Title: Formation and persistence of DNA, RNA, and protein adducts in mouse skin exposed to pure optical enantiomers of 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyre ne in vivo.
    Author: Pelling JC, Slaga TJ, DiGiovanni J.
    Journal: Cancer Res; 1984 Mar; 44(3):1081-6. PubMed ID: 6198079.
    Abstract:
    The covalent binding of (+)-anti-benzo(a)pyrene-7,8-diol-9,10-epoxide [(+)-anti-BPDE], the carcinogenic metabolite of benzo(a)pyrene, and its noncarcinogenic (-) enantiomer to macromolecules was investigated in mouse skin in vivo. Levels of the adducts were measured in DNA samples isolated from the epidermis of adult Sencar mice exposed topically to (+)- and (-)-anti-BPDE for 3, 24, and 72 hr. The amount of (+)-anti-BPDE bound to epidermal DNA was approximately 3 times higher than that of the (-) enantiomer at all time points studied, with the highest level of adducts observed after 3 hr exposure. A similar time course of binding was observed in DNA purified from epidermal basal cells which were isolated from mice treated with the two enantiomers. As with the results for isolated DNA samples from whole epidermis, we also observed a 3:1 ratio of binding with (+)- and (-)-anti-BPDE in basal cell DNA. Interestingly, no significant difference in total binding between the (+) and (-) enantiomers could be detected at any time point in RNA and protein isolated from the basal cells. The formation of individual DNA adducts derived from topically applied (+)- or (-)-anti-BPDE was monitored at 3, 24, and 72 hr using high-pressure liquid chromatography. The major DNA adduct (64% of total) formed from (+)-anti-BPDE cochromatographed with marker adducts of N2-[10S-[7R,8S,9R-trihydroxy-7,8,9,10-tetrahydrobenzo(a)pyrene]yl] deoxyguanosine, while other minor adducts also were observed. With the (-)-anti-BPDE, a greater variety of DNA adducts was formed, with only 20 to 30% of the radioactivity present in high-pressure liquid chromatography chromatograms corresponding to the N2-deoxyguanosine adduct. The rate of formation and disappearance of individual adducts derived from both isomers of anti-BPDE was similar over the 72-hr time course. The results suggest that, although differences exist in total binding to DNA between the two enantiomers, they do not appear to be of sufficient magnitude to explain the marked difference in biological activity of (+)- and (-)-anti-BPDE in mouse skin.
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